Contaminated urban agriculture sites are increasingly of concern for local regulatory authorities, with tensions between protecting public health from exposure to contaminated land and crops and supporting urban gardening as a health promoting activity. With the UK Environment Agency lowering the blood Pb level (BLL) used in the derivation of recommended ‘safe‘ soil guideline values to 3.5 µg/dL in 2014, the Newcastle Allotments Biomonitoring Project was initiated. The aim of this study was to investigate the relationship between the BLL of gardeners compared to their non-gardening neighbours along with a range of related and confounding variables. Soil, crops and participants blood and saliva samples were collected. Gardeners blood lead levels (BLL) ranged from 0.6 – 4.1 ug/dL. Percentage bioaccessibilities (and geomean total soil Pb), ranged from 32%–76% (338 mg/kg). Pb uptake in crops varied with crop type, highlighting soil plant concentration factors (SPCFs) as a key driver of exposure in urban gardening. Crops suitable for growing at allotments with elevated Pb were tubers, shrub and tree fruit with observed mean Pb concentrations <0.02 mg/kg FW. Crops less suitable for gardens with raised soil Pb were root vegetables, such as beetroot, parsnips, carrots and rhubarb, with observed Pb concentrations > 0.1 mg/kg FW. The extent to which the soil Pb is available for crop uptake, and the bioaccessibility, can be understood in terms of the solid-phase partitioning of the Pb following application of the Chemometric Identification of Substrates and Element Distribution protocol (CISED). The CISED extraction identifies the main acid soluble substrates in the soil and the fractionation of the Pb between them. This information is used in conjunction with soil properties to provide a holistic overview of the factors controlling the mobility of lead in the three allotment sites. The CISED mineral acid extractable Pb is between 75-85% for all soils. The majority of the soils show a dominating Pb component which also contains Al and P and suggests the presence of the mineral plumbogummite (PbAl3(PO4)2(OH)5·H2O). After weathering, Pb entering into soil from different Pb sources forms plumbogummite as a stable end point. Despite plumbogummite having low aqueous solubility these findings suggest it is the main source of bioaccessible Pb in these soils. Our work highlights the need to model exposure of specific sub-populations (such as urban gardeners) if we are to provide a robust, relevant and applicable soil screening value for soil Pb at such sites. This is essential if we are to provide confidence to regulators, who must decide on the suitability of a site, but also to the residents.